Why “x”?

But when the talk is about both math and linguistics, how could I resist? So I just had to watch Terry Moore’s four-minute TED talk on “why is x the unknown?” You should watch it too.

[time to let you watch the talk]

Now that you’ve watched it — now that you know why we use the letter x to represent the unknown — let’s look at the incorrect info. We can start with the claim that “Arabic…turns out to be a supremely logical language.” Any linguist will tell you that that’s sheer nonsense. Every language is supremely logical, although the logic will vary from language to language.

But even if you accept Moore’s flawed premise, you must then wonder about his conclusion that “that’s one of the reasonsso much of what we’ve come to think ofas Western science and mathematics and engineeringwas really worked out in the first few centuries of the Common Eraby the Persians and the Arabs and the Turks.” We have here three kinds of languages from three different language families — Farsi is Indo-European, Arabic is Semitic, and Turkish is of course Turkic — so why would the so-called logic of Arabic be relevant?

Then we get a more serious error. Moore claims that the Greek letter chi (χ) represents the “ck” sound. But it doesn’t! It represents the “ch” sound, as in the German “ach.” And supposedly that letter (close to “x”) was chosen in Latin because it looks like χ. Maybe.

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About me

I am starting my 21st year as a math teacher at Weston High School (the only public high school in Weston, MA, though sometimes it seems more like a private school). This is my 44th year as a teacher altogether. I also teach at Harvard’s Crimson Summer Academy each summer (this was the 15th!), and for 21 years I taught at the Saturday Course in Milton, MA. Until recently I served on the board of the Dorchester Historical Society.

I read, cook, and build my model railroad when I can. For some reason I’m left with less free time than would be ideal, but somehow I also manage to devote time to my wife, Barbara, and to our excessive number of cats.